This invention relates to preparing crystalline substrates useful for optical waveguides.
Crystalline LiNbO3 and LiTaO3 are used in optical waveguides. Integrated optic circuits based upon such optical waveguides are useful in various electrooptical devices including, e.g., fiber optic gyros (FOGs), photonic switching devices, and intensity/phase modulation systems. A variety of methods exist for fabricating LiNbO3 and LiTaO3 integrated optic circuits. Examples of these methods include localized diffusion of hydrogen into a LiNbO3 or LiTaO3 substrate, and proton exchange with the lithium present in the LiNbO3 or LiTaO3 substrate. These methods alter one or more refractive indices (e.g., the extraordinary and ordinary refractive indices) of the substrate in the region containing the diffused hydrogen to produce an optical waveguide.
During fabrication of the optical waveguide, protons replace the lithium atoms of the crystal structure. These protons are relatively small in comparison to the lithium atom and thus tend to move about the crystal structure of the waveguide. As a result, optical waveguides, the refractive index, and the region of guide itself tend to drift over time, which alters the output intensity of the waveguide. The waveguides must then be reset or recalibrated to correct for drift.
In one aspect, the invention features a method for manufacturing an article. The method includes contacting a crystalline substrate with a source of deuterium ions to create a region in the crystalline substrate having a crystal structure that includes deuterium ions. The region is capable of constraining a propagating wave to the region. In one embodiment, the crystalline substrate has a first refractive index and the region has a second refractive index. The second refractive index being different from the first refractive index. In preferred embodiments, the substrate is LiNbO3 or LiTaO3.
In one embodiment, the article is an optical waveguide.
In other preferred embodiments, the method further includes annealing the substrate. In another embodiment, the method further includes depositing an electrode pattern on the crystalline substrate. The electrode pattern is capable of modulating a wave propagating through the region.
In one embodiment, the invention features a method for manufacturing an optical waveguide. The method includes contacting a crystalline substrate having a refractive index with a source of deuterium ions to create a region that includes deuterium ions, and annealing the crystalline substrate for a time and at a temperature sufficient to create an optical waveguide. In preferred embodiments, the region has a refractive index different from the refractive index of the crystalline substrate.
In another aspect, the invention features an article that includes a crystalline substrate that includes a region that includes deuterium ions. The region is capable of constraining a propagating wave to the region. Preferred substrates include LiNbO3 and LiTaO3. In one embodiment, the crystalline substrate has a first refractive index and the region has a second refractive index. The second refractive index of the region is different from the first refractive index of the crystalline substrate. In other embodiments, the region is capable of constraining a propagating optical wave to the region.
In preferred embodiments, the article is an optical waveguide. In one embodiment, the article is an integrated optic circuit. Preferably the integrated optic circuit comprises electrodes positioned to modulate a wave propagating through said article. In other embodiments, the region is capable of supporting transverse magnetic propagation of a wave, transverse electric propagation of a wave, or both transverse magnetic propagation of a wave and transverse electric propagation of a wave.
In other aspects, the invention features a method for manufacturing an article. The method includes contacting a crystalline substrate with a source of tritium ions to create a region in the crystalline substrate having a crystal structure that includes tritium ions. The region is capable of constraining a propagating wave to the region.
In other aspects, the present invention is directed to the calculation, storage and retrieval of data for determining the depth of diffusion of lithium displacing ions in a crystalline substrate that includes lithium ions, and for use in a method for fabricating an optical waveguide. The data and control processes of the invention can be implemented by a software application program executed in a general purpose computing system and in combination with an ion bath.
The data and control processes of the invention can be embodied in a lithium ion displacing diffusion process implemented via the application program and also in an article of manufacture, in the form of a data storage medium that stores application program code arranged to carry out that method upon execution by a processor.
The optical waveguides of the invention are relatively optically and electrically stable such that they exhibit minimal thermal and electrical field drift.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.